Field of the Invention
The present invention relates to a control apparatus, a radiation imaging apparatus, a radiation imaging system, a control method of the radiation imaging apparatus, and a storage medium.
Description of the Related Art
There has been commercially available a radiation imaging system using a radiation generating apparatus for irradiating an object with radiation, a radiation imaging apparatus for generating a clear radiation image by performing image processing for a radiation image obtained by digitizing a radiation image which is the intensity distribution of radiation, and an image processing apparatus. Such a radiation imaging system transfers, to the image processing apparatus such as a control computer for image processing and storage, radiation image data obtained by the radiation imaging apparatus upon causing the radiation generating apparatus to irradiate an object with radiation. The image processing apparatus displays an image having undergone image processing on a display device such as a display.
The radiation imaging apparatus is formed by stacking a scintillator on a photoelectric conversion device (conversion device) for converting radiation into an image signal electric charge (an electric signal), and the like. The radiation imaging apparatus converts radiation into visible light through the scintillator, holds the visible light as electric charges, and forms an image from the amount of readout electric charges. The radiation imaging apparatus which forms an image from the amount of electric charges requires a lapse of a given time after energization of a circuit for driving the conversion device to enter an imaging enable state for image quality stabilization.
For example, Japanese Patent Laid-Open No. 2010-273858 discloses a method of saving power by shortening the time to enable imaging. To shorten the time to enable imaging, Japanese Patent Laid-Open No. 2010-273858 proposes a method of changing the timeout time after energization of a circuit for setting an imaging enable state, in accordance with the input state of patient information and an imaging protocol.
In a conventional radiation imaging system, the timing of radiation generation by a radiation generating apparatus is synchronized with the timing of imaging by a radiation imaging apparatus by performing communication between the radiation generating apparatus and the radiation imaging apparatus, and then the radiation imaging apparatus performs imaging. Recently, however, as disclosed in Japanese Patent Laid-Open No. 2009-219538, to simplify a system arrangement required for communication, a radiation imaging system which adopts a scheme of performing imaging immediately after detection of radiation in the radiation imaging apparatus without performing communication between a radiation generating apparatus and a radiation imaging apparatus has been developed. In this radiation imaging system, if an attempt is made to ensure a wide dynamic range which covers from a low radiation dose to a high radiation dose, a circuit for driving a conversion device or another electric circuit element unwantedly generates noise such as thermal noise and shot noise. Therefore, the S/N ratio decreases especially in a low-radiation-dose region, thereby deteriorating the image quality of an obtained radiation image. If a sensor is set in an imaging enable state for a given time or longer, the influence of noise becomes large. For this reason, noise is reduced by stopping driving of the sensor to set an imaging disable state (sleep mode) and to reset electric charges accumulated in the conversion device, thereby suppressing deterioration in image quality.
According to the method described in Japanese Patent Laid-Open No. 2010-273858, if it takes time to input patient information and an imaging protocol, the remaining time for actual imaging shortens. For example, timeout may occur during adjustment of the respiratory timing of a patient, resulting in an imaging disable state. This requires a given waiting time to set an imaging enable state again.
In addition, according to Japanese Patent Laid-Open No. 2009-219538, if radiation irradiation is performed without noticing that driving of the sensor stops to set an imaging disable state, desired radiation imaging may fail (misshooting).